1. Field of the Invention
The present invention relates to a work cutting apparatus and a method for cutting a work, and specifically to a work cutting apparatus and a method for cutting a sintered compact such as a magnet.
2. Description of the Related Art
FIG. 22 shows a conventional work cutting apparatus for obtaining a magnet used in a voice coil motor for example. This work cutting apparatus 1 is an overhang model of a so-called cantilever type. A rotating shaft 2 is mounted with a plurality of cutting blades 3 spaced from each other by spacers (not illustrated). The rotating shaft 2 has an end portion supported by a support arm 4. The work cutting apparatus 1 includes an X-slider 6 slidably placed on rails 5. The X-slider 6 has an upper surface provided with a chuck table 7. The chuck table 7 has an upper surface provided with a pasting board 8. The pasting board 8 has an upper surface placed for example with a plurality of works 9 fixed by an adhesive. Then, the X-slider 6 is slid in a direction shown by an arrow A (along an X axis), so that the works 9 are moved at a constant speed toward the cutting blades 3 rotating in a direction shown by an arrow B, thereby cutting the works 9 into a predetermined thickness. Since the works 9 are cut by the plurality of cutting blades 3, a plurality of magnet pieces are obtained in a single cycle of cutting operation.
In the work cutting apparatus 1, the cutting blades 3 should ideally be mounted at exact right angle to the rotating shaft 2. In such a case, a cutting reaction will only develop within surfaces of the cutting blades, or no force causing the cutting blade 3 to deform vertically to a rotating plane of the cutting blade 3 is generated. Actually however, as shown in FIG. 23, there is involved a cutting blade mounting error xcex8 (xcex8=0.02-0.04 degree approx.), and therefore the cutting reaction f. The cutting reaction f includes a tangential component force f1, which includes a component force f2 corresponding to the mounting error (f2=f1xc3x97sin xcex8) acting as the force to deform the cutting blade 3. As a result, the cutting blade 3 is deformed, and cutting accuracy is reduced.
Further, according to the convention, as shown in FIG. 24, a stroke L2 of the cutting blade 3 necessary for the cutting is long, and therefore a long time is required for the cutting operation, posing a problem of poor operability.
It is therefore a primary object of the present invention to provide a work cutting apparatus and a method for cutting a work capable of improving the cutting accuracy and productivity.
According to an aspect of the present invention, there is provided a work cutting apparatus for cutting a work by rotation of a cutting blade, comprising: a first driving portion rotating the cutting blade, and a second driving portion moving at least either one of the cutting blade and the work relative to the other in the vertical direction when cutting.
According to another aspect of the present invention, there is provided a method for cutting a work, comprising: a first step of placing the work at a predetermined position; a second step of preparing a cutting blade; and a third step of rotating the cutting blade, moving at least either one of the cutting blade and the work relative to the other in the vertical direction, whereby cutting the work with the cutting blade.
According to the present invention, by a cutting through lowering the rotating cutting blade for example down to the work disposed at a predetermined position, it becomes possible to reduce the force that deforms the cutting blade than in the convention. Thus, load acting on the cutting blade becomes smaller, deformation of the cutting blade becomes smaller, resulting in improved accuracy of a cut surface. Further, since a stroke of the cutting blade necessary for the cutting can also be reduced, cutting time can be reduced, and productivity is improved.
According to still another aspect of the present invention, there is provided a work cutting apparatus for cutting a work by rotation of a cutting blade, comprising: a first driving portion rotating the cutting blade, and a second driving portion moving at least either one of the cutting blade and the work relative to the other along a normal line passing the point of contact between the cutting blade and the work when cutting.
According to another aspect of the present invention, there is provided a method for cutting a work, comprising: a first step of placing the work at a predetermined position; a second step of preparing a cutting blade; and a third step of rotating the cutting blade, moving at least either one of the cutting blade and the work relative to the other along a normal line passing the point of contact between the cutting blade, whereby cutting the work with the cutting blade.
In this case again, in which the cutting is made along a normal line passing the point of contact between the rotating cutting blade and the work disposed at a predetermined position, the load to the cutting blade becomes smaller. Therefore, deformation of the cutting blade becomes smaller, resulting in improved accuracy of the cut surface. Further, since the stroke of the cutting blade necessary for the cutting can also be reduced, the cutting time can be reduced, and productivity is improved.
According to the present invention, preferably, the cutting blade is mounted to a rotating shaft, and the rotating shaft has two end portions supported by a supporting portion mounted to a unit. By supporting at both end portions of the rotating shaft, it becomes possible to hold the cutting blade more stably, thereby reducing the deflection of the cutting blade during the cutting operation. Therefore, when cutting a brittle work such as a sintered compact, chipping can be reduced, and cutting accuracy can be improved. Further, since the deflection of the cutting blade can be reduced, the number of cutting blades to be mounted to the rotating shaft can be increased. As a result, the number of pieces obtained by a single cutting operation can be increased, and therefore productivity can be increased. Further, since the supporting portion supporting both end portions of the rotating shaft is mounted to one unit, holding accuracy of the cutting blade, particularly horizontal accuracy can be improved.
Further, preferably, the supporting portion includes a first supporting portion and a second supporting portion respectively supporting the two end portions of the rotating shaft. The first supporting portion is mounted movably to the second supporting portion.
Further, preferably, the rotating portion includes an arbor having two tapered end portions, and rotation supporting portions each having a receiving portion mated with one of the tapered end portions of the arbor. By forming the taper at each end portion of the arbor of the rotating shaft, and by mating each tapered end portion to the receiving portion, fixing accuracy of the cutting blade can be improved.
Further, preferably, the first driving portion includes a belt for rotating the cutting blade by belt transmission, and a tension adjusting portion for adjusting tension of the belt. By maintaining the tension of the belt always at a constant level by the tension adjusting portion, slippage of the belt can be prevented, and rotation of the belt can be stabilized. This is particularly effective in an arrangement in which the cutting is made by moving the cutting blade toward the work.
According to the present invention, preferably, a plurality of works are disposed on a recess of a work disposing portion. With such an arrangement, a large number of works can be cut at one time.
Further, preferably, the recess has a V-shaped section in at least either one of a plane including the cutting blade and a plane parallel thereto. By making the recess to have the V-shaped section, cost of machining the work disposing portion can be reduced, and applicability to a variety of kinds of works is achieved. Especially, a plate-like work can be positioned stably without rattling.
Further, preferably, the cutting blade include a disc-like substrate having a Young""s modulus of 441,315 N/mm2xcx9c686,490 N/mm2, and a cutting edge formed in an outer circumference of the substrate. By using a super hard metal for example, having the Young""s modulus of 441,315 N/mm2xcx9c686,490 N/mm2, as the substrate of the cutting blade, a cutting blade which is thin, hard and cuts well can be obtained. Therefore, margin allowed for the cutting blade can be narrowed, yield of products can be improved, and productivity can be improved.
Preferably, the apparatus further comprises a fixing member for fixing the work to the recess. The fixing member has a comb-like portion pressed to a surface of the work facing the cutting blade. According to this arrangement, since the work is fixed by the comb-like portion pressed from above to the surface of the work facing the cutting blade, differing from the convention, there is no need for bonding the work by adhesive and so on or un-bonding the adhesive after the work is cut, leading to reduced operation time and improved productivity.
Further, preferably, a plurality of the cutting blades are included into a cutting blade block. The cutting blade block have two end portions each mounted with a cutting blade having a thickness greater than a thickness of the other cutting blades. By increasing the thickness of the cutting blades at the ends, each end margin of the work potentially becoming a dimensionally inferior product can be ground into dust. Therefore, inclusion of the inferior products can be prevented, and yield and productivity can be improved.
Further, preferably, a plurality of cutting blade blocks are mounted axially thereof. According to this arrangement, a mounting error in each of the cutting blades will not adversely affect adjacent cutting blade blocks, or the error will not accumulate. Therefore, a plurality of cutting blade blocks can be axially disposed, and as a result, a greater number of works can be cut in a single cutting operation. Further, since the cutting blade block can be set for each of the works, mounting accuracy of the cutting blade can be improved, and inclusion of dimensionally inferior products can be reduced. Therefore, yield is increased, and productivity is improved.
According to the present invention, preferably, the apparatus further comprises a first coolant supplying portion including a first supplying port and a second supplying port each supplying a coolant to the works. By providing the first supplying port and the second supplying port each discharging the coolant from a position different from the other, thereby supplying the coolant to the works from the plurality of locations, the coolant can be supplied reliably even if the work disposing portion having the recess is used and the cutting blade has an increased area of contact with the works. Therefore, the cutting blade can be abraded efficiently, making possible to cut the works productively.
Further, preferably, the first supplying port is formed near the works, whereas the second supplying port is formed on an upstream side of rotation of the cutting blade than is the first supplying port. According to this arrangement, since the coolant is supplied to the cutting blade and the works from the same side thereof and from the plurality of locations, sludge can be discharged smoothly.
Further, preferably, the plurality of works are disposed on an upstream side and an downstream side of the rotation of the cutting blade, and the coolant from the second supplying port is directed toward the work on the downstream side of rotation of the cutting blade. According to this arrangement, the coolant can be supplied also to the work located on the downstream side of rotation of the cutting blade. Further, the coolant from the second supplying port interrupts an accompanying stream of air which follows the turning of the cutting blade. Therefore, the coolant from the first supply port becomes less affected by the accompanying stream of air, and therefore the coolant from the first supplying port can be supplied more reliably to the works.
Preferably, the apparatus further comprises a second coolant supplying portion including a supplying port formed in the recess for supplying the coolant. According to this arrangement, the coolant can be supplied to portions where the first coolant supplying portion can not efficiently supply the coolant such as a side surface of the work. Thus, cutting accuracy of the work is improved further. This arrangement is especially effective if the work has a large thickness.
Further, preferably, the apparatus further comprises an enclosing member enclosing the recess. According to this arrangement, it becomes possible to hold the coolant in the recess. Thus, the work can be cut while the work is being bathed in the coolant. Thus, the cutting accuracy of the work can be further improved.
Further, preferably, the cutting blade includes resin-bound diamond. If the cutting blade includes resin-bound diamond, insufficient amount of supply of the coolant will cause abnormal friction in the cutting blade, deteriorating the cutting accuracy. Thus, the present invention is especially effective.
Preferably, a discharge pressure of the coolant is 196,140 Paxcx9c471,050 Pa. According to this arrangement, the cutting blade including the resin-bound diamond can be abraded efficiently, making possible to cut the work smoothly.